The present invention relates to a gas generator for use in an air bag apparatus for inflating an air bag or a pretensioner for winding up a sheet belt, which saves a driver and a passenger in a vehicle. The present invention also relates to a gas generating composition which is of a low-temperature ignition type, and which is used in a gas generator.
A conventional gas generator for air bag or pretensioner is filled with a gas generating agent comprised mainly of sodium azide and various oxidizing agents. However, sodium azide has high toxicity and poor handling properties, and therefore there are demands for development of a gas generating agent using no sodium azide.
As a first prior art, International Publication No. WO98/47836 discloses a gas generating agent consisting of ammonium perchlorate, a chlorine scavenger, and an organic fuel component. This gas generating agent has low toxicity and excellent long-term stability, and further such excellent stability at high temperatures that the heating starting temperature is 300° C. or higher.
In recent years, for achieving a lightweight gas generator, an aluminum container is used in the gas generator as a substitute for a stainless steel container. The aluminum container has a problem that it has an extremely low strength at high temperatures, as compared to the stainless steel container. Therefore, there is a fear that, when a vehicle is exposed to a high temperature atmosphere due to, for example, fire, the aluminum container cannot endure the combustion pressure caused by combustion of the gas generating agent and bursts. For this reason, it is difficult to use the gas generating agent of the first prior art for filling an aluminum container.
Thus, there are demands for development of a gas generating agent that can be used for filling an aluminum container without any problem. Specifically, there is demanded a gas generating agent that ignites by itself at a temperature lower than the temperature at which the strength of the aluminum container begins to lower, more specifically at a temperature in the range of from 170 to 220° C., so as not to cause the aluminum container to burst.